The publication FR-A-425,184 describes an installation for the disinfection of water wherein UV irradiation apparatus is arranged overground in the course of a conduit connecting a high-level reservoir to a lower-level reservoir. This installation works without power consumption for feeding the water if the water flows from said high-level reservoir to said lower-level reservoir and if the fall of water is sufficient for generating the necessary water throughput in the UV irradiation apparatus. However, if the fall of water is slight, as this is generally true for conduit tubes, the water to be treated must be fed with energy consumption to a UV irradiation apparatus arranged overground.
The publication FR-A-421,296 describes an installation of the same kind wherein the water to be treated is conveyed through a conduit arranged overground and provided with a UV irradiation apparatus by the water pressure in the feeding conduit. In addition to the energy consumption which is necessary, this apparatus has the drawback that the overpressure in the conduit, in combination with the proposed replaceable UV radiator units, causes enormous sealing problems. Moreover, for replacing the UV radiator units, the installation must be shut down, i.e. the water flow must be interrupted.
Therefore, installations of this kind were developed which can be operated without additional energy consumption.
In the conventional installations of this kind, the UV irradiation apparatus is built into the waste conduit. The individual UV radiators are surrounded by radiation pervious protective tubes which are intended to prevent an access of water to said UV radiators. Usually, the installation comprises a plurality of UV radiators which are grouped, together with their individual protective tubes, so as to form modular, individually replaceable kits. These kits are arranged in the waste conduit in such a manner that the UV radiators or their protective tubes, respectively, one completely immersed in the sewage. The upper ends of said kits are provided with the electric fittings necessary for operating the UV radiators, said electric fittings being connected to an electric supply unit by means of plug-type connectors (cf. e.g. the publication EP-A2-0,317,735).
Disinfection installations of this kind have various drawbacks. In the waste conduit, supporting facilities for the UV kits must be provided comprising guides for assembling and disassembling the former. In consideration of the low sewage level, which is about half a meter below the ground level, said guides are considerably long. A further problem is that of reliably and durably sealing said supporting facilities against the conduit wall in order to prevent any sewage from flowing past the UV kits. Inundation of electric fittings having electric insulation defects, e.g. under unfavourable weather factors, and leakages of the protective tube holders may bring electric installation parts into contact with water thus resulting in operating troubles. The danger of damages is increased, if assistant staff is engaged for supervising the disinfection installation, as is usually done. A further drawback is that the protective tubes of UV kits in action can only be cleaned mechanically, which in many cases is not sufficient for removing the coating which has formed on the outer surfaces of the protective tubes. For a more efficient chemical cleaning, the UV kits must be disassembled, since otherwise the cleaning fluid could get directly into the sewage.
The publications FR-A-433,368 and DE-A-2,213,658 describe installations for the treatment of water by means of UV radiation, wherein the UV kits are arranged in containers to which the water to be treated is fed in a free flow. However, the difficulties occuring in the installation according to the publication EP-A2-0,317,735 described above, can be removed only to a small extent.